ABSTRACT Transwomen Connected: a mobile app delivered HIV prevention program During the past two decades, the HIV epidemic has severely impacted transgender women in the U.S. Analysis of 2013 national HIV testing data found that transgender persons have the highest HIV incidence of any risk group, and discrepancies between self-reported prevalence and HIV testing data indicate that many HIV-infected transgender women are not aware of their HIV status. Other public health conditions among transgender women include discrimination-based physical and verbal abuse, poor mental health, alcohol and drug use, and unmet health care needs resulting from limited healthcare access and negative healthcare encounters. These co- occurring problems additively increase sexual risk for transgender women. Despite these health disparities and health-care access barriers, the U.S. National HIV/AIDS Strategy notes that HIV prevention efforts specifically targeting transgender populations have been minimal. In particular, there are no transgender-specific, evidence- based programs that address the unique prevention needs of transgender women, leaving practitioners to implement programs designed for men who have sex with men (MSM) or cisgender women, even though transgender women's experiences of gender abuse, gender transition, transactional sex and violence distinguish them from most MSM and cisgender women. This project will address these gaps and fill an important product niche by testing the feasibility of creating Transwomen Connected: A Sexual Health Promotion Mobile App designed to engage transgender women through a strengths-based approach to HIV prevention and sexual health that uses the power of social networks to identify and encourage protective factors that support the health and well-being of transgender women. The mobile delivered intervention will expand the HIV prevention opportunities for transgender women by (1) providing organizations a cost-effective and easily implementable intervention option that is specifically designed for transgender women; (2) not requiring participants to attend multiple face-to-face sessions in a physical location and instead support iterative intervention implementation at any time or place; (3) permit transgender women to anonymously view the program on their phone in private settings; and (4) offer practitioners and agencies with low levels of technological infrastructure an effective means to connect with clients via mobile technology. The Phase I project, guided by an expert panel of transgender women of color, will produce: extensive formative research; a complete curriculum outline developed using a holistic, sexual harm reduction and life skills framework based on Social Cognitive Theory, gender affirmation, social support, and resilience; a prototype mobile app with complete app design, architecture, and three activities; and a usability evaluation to determine usability, appeal, and impact on knowledge and attitudes. Phase II will complete development and conduct a multi-site randomized controlled trial to assess effectiveness.